Black Storm-Petrel vs Markham's Storm-Petrel

The Black Storm-Petrel and Markham's Storm-Petrel are both dark, medium-sized storm-petrels, but they can be distinguished by their tail shape and flight style. The Black Storm-Petrel has a more deeply forked tail and a distinctive bounding flight, while Markham's Storm-Petrel has a shallower fork and a more gliding flight pattern.

Look for the tail shape: Black Storm-Petrel has a deeper fork. Observe the flight style: Black Storm-Petrel has a bounding flight, while Markham's Storm-Petrel glides more. Consider the geographic location: Black Storm-Petrel is more likely in the Gulf of California, whereas Markham's is associated with the Atacama Desert.

Both species are similar in size, with the Black Storm-Petrel being slightly larger.

Both species are predominantly dark, but the Black Storm-Petrel may appear slightly darker overall. The tail of the Black Storm-Petrel is more deeply forked compared to the shallower fork of Markham's Storm-Petrel.

The Black Storm-Petrel exhibits a bounding flight with rapid wingbeats, whereas Markham's Storm-Petrel tends to glide more smoothly.

Black Storm-Petrels are often found in the Gulf of California and along the Pacific coast of Baja California, while Markham's Storm-Petrels are more associated with the Atacama Desert region and are affected by light pollution there.